International Journal of Physics and Astronomy

Photo Absorption in Gel Grown Strontium Oxalate Single Crystals
P V Dalal, M P Deshpande

Abstract
Strontium oxalate crystals have been grown by simple gel technique using agar gel as the growth medium at ambient temperature. The slow and controlled reaction between strontium chloride and oxalic acid in agar gel has formed strontium oxalate. Optical absorption spectra of these grown crystals are recorded in the wavelength region from 200 to 800 nm. The particular range 200 to 350 nm is important because it only yields the necessary information. The absorption spectra reveal transitions, involving absorption and emission of phonons and also show that the crystal is transparent in the region 500 to 800 nm. The detail study supports the existence of forbidden indirect transition in the material. The forbidden indirect transitions in crystals are found to be 0.058eV and 0.078eV, and these correspond to 262.8 nm and 326 nm respectively as internal vibrations. Different segment of a1/3 vs hn graph were used to distinguish individual contribution of phonons and scattering of charge carriers in the lattice and it is found due to acoustic phonons.

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